This invention relates to a method for determining a supplementary amount of a developing solution for use in a film developer.
In a conventional automatic film developer, in order to compensate insufficient development of a photographic film, which is caused by fatigue of a developing solution, the fresh developing solution is replenished during the developing operation. The proper amount of the fresh developing solution supplemented should be in proportion to the total amount of a blackened silver compound reacted on the film processed, which is, in case of a lithographic film, in proportion to the total area of blackening to be produced on the film.
However, this total area of blackening to be reacted is in proportion to not only the size of the film but also its blackening area rate which depends on each reproduction picture exposed on the film. Therefore, it is difficult to determine the total blackening area.
In a conventional automatic film developer, the blackening area rate is determined by the experiences obtained by an operator, and then according to the blackening area rate and the area of the film the supplementary amount of the fresh developing solution is determined, or the blackening area of the film developed is photoelectrically measured, and then according to the value measured the appropriate amount of the developing solution is determined, or a film strip exposed by a certain amount of light is continuously developed, and then according to the lowering of the density of the film developed the suitable amount of the fresh developing solution is replenished.
In these conventional methods, however, the first method is not always reliable, and the latter two methods require expensive apparatus and lack in a quick response property.